Large format USB Hard Drive – 2tb, 3tb, 4tb showing in Disk Management but does not get drive letter in Windows 7 and Server 2008 r2. How to Solve…

We had a problem recently where we replaced the external backup drives on a client’s 2008 r2 server with a new suite of Samsung m3 portable 2tb USB 3.0 drives. The problem is that when the drives were plugged into the server on any USB port, they were detected as USB devices fine but did not appear in Windows Explorer. We checked in Disk Management and the drives appear ok but do not offer a drive letter. Also, the only option when right-clicking on the drive in Disk Management is to convert to a dynamic disk. There is no option to change drive letter.


After some research it was determined that the physical sector size on these drives was 4KB. Drives with physical sector size of 4KB represent the latest technology and as they are transitioning from the traditional 512 byte sectors which has existed since drives were measured in megabytes. The physical sector size represents the smallest unit that will be consumed even when the file being written is smaller. Years ago it would matter if a few Kilobytes were wasted but as the size of storage drives continually expanding, it makes sense for the physical sector size to grow too. A larger physical sector size means less error checking (ECC) required and therefore faster access.

It turns out that a lot of these Advanced Format Disk that have a 4KB physical sector size do still have the capability to be backwards compatible with 512 byte physical sector size systems. They do this by changing their logical addressing system to 512 bytes although their physical sectors remain at 4k. They are known as 512-byte emulation disks.

We did a check of the drives using FSUtil on a windows 8 machine which supports these drives natively…

Fsutil fsinfo ntfsinfo [driveletter]

It shows the Physical and logical “Bytes per sector” value. The drives we had were emulation disks.


Apparently this Server 2008 r2 had some issues seeing these drives properly. To solve this issue we installed the…

Microsoft KB 982018 – An update that improves the compatibility of Windows 7 and Windows Server 2008 R2 with Advanced Format Disks is available

and rebooted the server. The drives magically appeared with a drive letter and the correct sizing for 2tb.

The strange thing is that this update is supposed to be contained within SP1 of Server 2008 r2 which this server already had. Maybe the USB subsystem just needed to be reset in some way that this update helped with. In any case – if you are addressing this problem it might be worth a try!


Authored by Ian


Ian Johnson is a Director of OJ Networks. He has been working in IT since 1995. Mentored by the best, Ian started as Technical Support Officer for an innovative dialup ISP in Brisbane “Hub Communications”. He progressed to become a Web Design and Programmer in ASP, ASP.NET and PHP during his time at “The Lab Development Group” with David Vandenberg amonst others. Ian has been working as a Consultant on the Sunshine Coast since 2001 and became a Microsoft Certified Information Technology Professional (MCITP) Server Administrator in 2010 after which he formed OJ Networks. He has assisted numerous small businesses to reach their potential through IT Infrastructure Planning and Implementation and Web design, Development and Web Marketing. You can connect with Ian on Linked In.

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